Treating livestock and game animals to control ticks, biting flies, and similar haematophagous or noxious arthropods or other parasitic pests is essential to prevent major economic losses. Typically, these parasites pierce the skin of animals, causing damage to the hides, blood loss, and irritation, as well as transmission of deadly infectious diseases. These factors contribute to the enormous economic losses sustained by the livestock industry. Losses in livestock production (cattle, sheep, swine, and poultry) in the U.S. due to arthropod pests have been estimated at more than $3 billion. This figure does not include the cost of pest control or losses to the equine industry (Drummond, R. O., J. E. George, S. E. Kunz 1988! Control of Arthropod Press of Livestock: a Review of Technology, CRC Press, Inc., Boca Raton, Fla., 245 pp.). Although precise figures for most countries are lacking, estimates of world-wide economic losses due to ticks and tick-borne diseases alone are in the billions of dollars.
Ticks affect approximately 800 million cattle and a similar number of sheep throughout the world (Sutherst, R. W., R. J. Jones, H. J. Schnitzerling 1982! Nature(London) 295:320-322). McCosker (McCosker, P. J. 1979! "Global aspects of the management and control of ticks of veterinary importance," In Recent Adv. Acarology, Rodriguez, J. D. (ed.), 2:45-53) estimated the world-wide impact of tick-borne diseases of cattle at approximately $7 billion. In addition to transmission of diseases, ticks cause severe damage due to failure of cattle to achieve expected weight gains and damage to hides to be used for leather. According to Norval (Norval, R. A. I. 1990! Parasitologia 32:155-163), weight losses in cattle are estimated at 4.4 grams per Rhipicephalus appendiculatus female and 10 grams per Amblyomma hebraeum female. Estimates of losses in wildlife are unavailable; however, tick infestations of white-tailed deer (Odocoileus virginianus) in some areas are so severe that they have been reported to kill fawns (Drummond et al., supra).
Treatment or prevention of insect and tick infestations on animals, especially animals in the wild, is a formidable task. Thus, it is not surprising that no single, universally accepted method is available for this purpose. Common practices for delivering a pesticide, e.g., an insecticide or an acaricide, to livestock include (1) direct, whole-body treatment, where the animal's body is drenched with pesticide-containing liquids; (2) systemics, where the pesticide is allowed to circulate in the host's blood; and (3) controlled-release systems, which are usually physically attached to the animal and which release pesticide continuously over a period of weeks or months.
There are disadvantageous features to all of these previously described methods. Whole body treatments involve substantial waste. In addition, for dipping or spraying, the animals must be herded and driven to, or through, the treatment area. Such procedures are both labor-intensive and stressful to the livestock. Moreover, due to the high potential for spillage, these operations pose significant environmental hazards for the surrounding area as well as health hazards for workers.
Systemics are generally not acceptable, especially for food animals, because of the toxic residues that can concentrate and remain in animal tissues for extended periods. Controlled-release devices, e.g., ear tags, risk infection or skin irritation when these devices are attached to the animal's body. None of these procedures are suitable for use with wildlife such as deer or other large herbivores.
An alternative to the methods described above is self-medication. In self-medication methods, an animal which is attracted to a device that offers a bait, e.g., food, materials for nest construction, etc., is sprayed or coated with pesticide-containing composition when the animal either contacts the device or in some way triggers the device to release the pesticide. Such methods offer an advantage over the previously described methods by minimizing the amounts of pesticide dispersed to the host and, consequently, into the environment.
One well-known example of a self-medicating device is the Duncan Applicator (ARIPO Patent No. AP/88/00079), which has been used to treat livestock and wild ungulates in Africa. The Duncan Applicator consists of a container placed on top of a tall, threaded rod which is placed in a bin containing feed. The overhead container releases an oily liquid pesticide mixture which slowly flows down the rod. When the animals place their heads in the bin to eat the feed, they touch the rod and receive a small amount of pesticide. The Duncan Applicator, due to its design, has limited utility for treating livestock and most wildlife. A principal disadvantage of the Duncan Applicator device is that the container at the top of the threaded rod is small and is exhausted in a short period of time, usually requiring the device to be recharged every day. Such high incidence of maintenance makes the Duncan Applicator difficult to use in areas which may be inconvenient to reach or inaccessible under inclement weather conditions. Further, daily recharging of the Duncan Applicator incurs a high labor cost, making the cost of using the device unattractive. Substituting a larger capacity container on the Duncan Applicator would not provide a complete remedy to the disadvantage of high maintenance. A larger capacity container would increase the tendency for the Duncan Applicator to tip over. If the device is tipped over, the result is a spill of the pesticide on the ground contaminating the environment. The Duncan Applicator poses an environmental threat since the pesticide is not contained and may easily be spilled if the Applicator is knocked over. Two scientific articles have been published relating to this Applicator (Duncan, I. M. (1992) "Tick control on cattle with flumethrin pour-on through a Duncan applicator" J.S. Afr. Vet. Assoc. 63:125-127 and Duncan, I. M., N. Monks (1992) "Tick control on eland (Taurotragus oryx) and buffalo (Syncerus caffer) with flumethrin 1% pour-on through a Duncan applicator" J.S. Afr. Vet. Assoc. 63:7-10).
Other variations of self-medicating devices have also been described. U.S. Pat. No. 3,870,023 describes an insecticide applicator for livestock which utilizes a wind-powered spray device. This clearly is distinguished from the subject invention, which does not use a spraying device to apply insecticide. Nor does the subject invention rely on wind power to dispense insecticide.
Other combination feeder/applicators include the inventions described in U.S. Pat. Nos. 3,137,274, 3,187,772, 3,941,096, 4,023,533, and 4,459,942. Each of these patents discloses a feeder to attract livestock and a means for dispensing insecticide which is operable when contacted by the animal. However, none of these patents describe a device which incorporates the elements of the subject invention.
U.S. Pat. No. 3,118,427 describes a "bunt bag" which dispenses liquid insecticide when the bag is contacted by an animal. The '427 device essentially uses an absorbent material to surround the liquid pesticide storage area. U.S. Pat. No. 3,159,144 uses gravity to transfer insecticide from a cable or chain core, saturated with pesticide, to absorbent discs which surround the core. These devices also have limited container capacity and require frequent maintenance.
The livestock oiler disclosed in U.S. Pat. No. 3,727,586 also dispenses insecticide when the animal contacts the device. The '586 patent employs a container which supplies pesticide by gravity to valves which open to dispense insecticide upon contact or rubbing of the valves by the animal. The apparatuses disclosed in U.S. Pat. No. 5,027,747 pertain to the use of absorbent wicks which contact an animal as it passes through a pathway.
The USDA/ARS has patented an apparatus for topical pesticide treatment of wildlife (U.S. Pat. No. 5,367,983). This device consists of four columns around two feed bins. The pesticide is stored in a container in the center of the unit, adding weight to an already substantially unwieldy contraption which is too heavy to be manually lifted.
U.S. Pat. No. 5,357,902 pertains to the UF self-medicating applicator of Norval, Meltzer, Sonenshine and Burridge. This applicator contains a container for pesticide storage as opposed to the disposable, self-contained column of the subject invention which allows facile, effortless recharging with treatment material. This applicator is the subject of the following scientific article: Sonenshine, D. E., Allan, S. A., Norval, R. A. I. and Burridge, M. J. (1996) "A self-medicating applicator for control of ticks on deer" Med. Vet. Entomol. 10:149-154.
It is therefore an object of the subject invention to provide an efficient, low-maintenance self-medicating applicator for wild animals and livestock, e.g., cattle, wild deer, etc. The self-medicating applicator of the subject invention can store an amount of pesticide sufficient to make the applicator maintenance-free for several days, weeks, or months, and dispense a liquid pesticide externally to an animal in such a manner as to treat the animal and thereby deter or kill dangerous, disease-transmitting ticks and other biting insects. As used herein, reference to "pesticide" includes chemical pesticides as well as entomopathic fungi, nematodes, and bacteria, and compounds such as growth regulators.